"Issue at hand, though, is whether or not using the subpanel grounding terminal bar as this 1/4" x 2" bar is a violation or not."

Is this bar in fact 1/4" thick, and 2" wide, and xx" long?

Ground blocks/bars are usually not 1/4" thick, 2" wide by xx" long.

I have to agree with Gregs first paragraph, in his response above.



John